Surveying the efficiency of Platanus orientalis bark as biosorbent for Ni and Cr(VI) removal from plating wastewater as a real sample.

Heavy metals make up one of the most important pollutants in industrial wastewater. For wastewater, adsorbent materials developed from suitable biomass can be effective in removing the heavy metal ions. In this study, the powder of the bark of Platanus orientalis was used as a biosorbent to remove Cr(VI) and Ni from a nickel-chromium plating wastewater as a real sample for the first time. Two different adsorbents were used in analyzing the data: modified and non-modified bark. The extent of adsorption was dependent on the pH (in the range of 1.5, 3, 5, 7, and 9), the time of contact (in the range of 30, 60, 90, 120 min), and the adsorbent dosage (different doses of 0.5, 1, 1.5, 2 g L^-1). The concentration of unabsorbed metals was measured by inductively coupled plasma-optical emission spectroscopy (ICP-OES, Model Thermo iCAP 6000). The maximum removal of Cr(VI) was obtained 89.6% for non-modified bark and 90.7% for modified bark both at pH of 5 in 2 g L^-1 of adsorbent dosage in 300 min. While, the maximum Ni removal was obtained 74.5 and 56.5% for non-modified and modified bark, respectively, at pH 3 in 2 g L^-1 adsorbent dosage in 90 min. Based on the results, Freundlich isotherm appears better fitted in adsorption with a better correlation coefficient (R² = 0.998) than that of Langmuir model with a correlation coefficient of R² = 0.996. The q_max for Ni₁ and Ni₂ were 126.58 and 285.714 mg g^-1 and the q_max for Cr₁ and Cr₂ were 13.423 and 19.920 mg g^-1, respectively. The FTIR studies indicated that S-O stretching group from sulfonate, surface O=H stretching, and also aliphatic C-H stretching are responsible for the adsorption. The SEM results obviously show the difference between the biomass surface before and after loading of ions. Ultimately, the present study concluded that P. orientalis could be a cheap and efficient biosorbent to adsorb and remove Cr(VI) and Ni from the plating wastewater; however, it seems more efficient for Cr(VI) with an average removal power of 90.15% than Ni with an average removal power of 65.75%.